1. Field of the Invention
The present invention relates generally to machine tools and, more particularly, to a machine tool with an automatic tool exchanger for exchanging a tool received in a tool spindle with another tool selected out of a tool magazine.
2. Description of the Prior Art
In a known machine tool of this kind, a drive key and a key-way complemental thereto are provided respectively on a tool spindle and each of the tools to transmit the driving force of the tool spindle to the tool received therein, and the tool spindle is arranged to be indexed to a predetermined angular position prior to a tool exchange operation. At tool holding portions of a tool magazine, there are provided detent members with which the key-ways of the tools are respectively snugly engaged, so as to prevent the tools from angularly moving even a little in the stored state. Furthermore, the drive key and the key-way are machined to almost the same width, such as, for example, the former being 25.4 mm. wide, the latter being 25.7 mm. wide, and thus, when engaged, to establish little clearance or play therebetween so as not to permit relative rotation between the tool spindle and the tool received by the same.
In the prior art machine tool, therefore, when the tool is presented onto the tool spindle, with its key-way not being exactly aligned with the drive key, the performance of an automatic tool exchange operation becomes impossible since, in such an event, the drive key necessarily interferes with a flange portion of the tool. This trouble occurs, though rarely, due to the fact that there appear many technical difficulties in exactly holding all of the tools stored within the tool magazine at the same angular position and also in presenting the tool to the tool spindle with its key-way being exactly aligned with the drive key.